DNA Testing

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Interested in learning about your ancestry? There’s never been a better time. The Internet makes it easy for amateur genealogists to research documents and connect with living relatives.

And now there’s an even more powerful tool you can use: direct-to-consumer DNA testing.

What Is DNA?

To answer this question, we need to go back to high school biology. (Don’t worry, we’ll make this as painless as possible.)

Your Genetic Blueprint

Deoxyribonucleic acid, or DNA, is a long chain of chemicals that’s found in the cell nuclei of almost all living things, from amoebas to plants to humans. Think of it as your personal blueprint. It tells your cells which proteins to synthesize in order to create the perfect you.

Ninety-nine percent of your genetic code is shared with your fellow humans (we all have one head and two eyes, for example). But 1 percent is unique to you. And that’s what DNA testing looks at.

Your Chromosomes

The DNA in your cell nuclei is coiled into threadlike structures called chromosomes. Regions on the chromosome that determine specific traits are called genes.

Each cell contains 23 pairs of chromosomes - one inherited from your father and one from your mother. But…

Sex cells (eggs and sperm) are a notable exception to this rule. They contain only one copy of each chromosome. When an egg and sperm unite, they form the first complete cell of a new person (which has 23 chromosome pairs).

One pair of chromosomes determines your biological sex. Possible combinations are XX (female) and XY (male). A woman can pass her X chromosomes to children of either sex. But the Y chromosome passes only from father to son. (More on that in a minute.)

Mitochondrial DNA

Outside your cell nuclei, DNA is found in only one other place in your body: mitochondria. The mitochondria are tiny energy-producing structures inside your cells. They contain a special kind of DNA inherited from your mother only.

Making New DNA

Cells reproduce by dividing. During this process, the DNA replicates to create an exact copy of itself for the daughter cell.

But there’s an important exception to this process. When the DNA of a sex cell (an egg or sperm) replicates, the new chromosomes often exchange pieces of DNA. This is called recombination, and it’s important to understanding the different types of DNA tests.

DNA Changes Over Time

Occasionally, DNA changes due to environmental factors or replication errors. This is called a mutation, and it’s often passed on to future generations.

Because mutations are unique, they’re quite useful in tracking a lineage over time.

How DNA Tests Work

DNA testing compares certain parts of your genetic code to known sequences (for example, a pattern commonly found in people with blue eyes).

Many companies also load your results into a database that can match you with relatives (often your distant cousins).

Testing can help you to:

1

Learn About Your Ancestors and Ethnic Heritage

Certain DNA sequences are more common in certain ethnic groups. Some kinds of tests can trace your origins back tens of thousands of years.

2

Learn About Your Health

DNA testing can tell you if you carry the gene for certain diseases, or whether you have a genetic predisposition to conditions like Alzheimer’s or Parkinson’s disease. Some tests also report on traits like obesity, baldness, and back hair.

While this can be interesting and useful, it also has limitations that will be important for you to keep in mind. So it’s always best to discuss the results of DNA health tests with your health care provider.

3

Find Living Relatives

Connecting with your living relatives brings the obvious benefit of fostering a broader sense of family. But finding relatives also allows you to compare family trees, solving puzzles in your family history.

How to Test

Each DNA testing company offers different tests and packages (more on that in a minute). Some specialize in certain ethnic groups, like lineages from Africa or the United Kingdom.

To get started, you’ll need to order a test kit. Then provide either a saliva sample or a cheek swab and send it back by mail. Results take six to 10 weeks to process (sometimes longer around the holidays).

A Word About Privacy

Once you take your test, your DNA profile will usually be added to the company’s database. In some cases, profiles are shared with researchers or sold for profit. (Identifying information is removed, but it’s always possible someone could identify you from your DNA alone.)

Some people like the idea of contributing to medical research. But if you have concerns, be sure to read and understand the testing company’s privacy policy. Some vendors never share or sell your information, and others allow you to opt out of these practices.

Types of DNA Tests

Testing companies offer a variety of DNA tests and packages, which can be super confusing when you’re staring out. So let’s look at the different test types and how they can help you.

Autosomal DNA Test

Learn about your recent ancestry across all lineages.

Who can take this test: everyone.

This test looks at markers on your 22 pairs of autosomal chromosomes (everything but your sex chromosomes). You inherited this information from all lines of your family - both parents, all four grandparents, all eight great-grandparents, and so on.

Autosomal DNA testing sequences about 700,000 single nucleotide polymorphisms (also known as SNPs, or snips). SNPs are little DNA sequences known to vary among individuals.

If you share a lot of SNPs with someone, there’s also a good chance that you have a common ancestor. For this reason, autosomal DNA testing can be a cost-effective way to connect with living relatives. And it can also give you a broad-strokes picture of your ethnicity.

The downside: autosomal testing only gives you useful information about the past few hundred years.

To put things in perspective, only 3 percent of your autosomal DNA comes from each great-great-great-grandparent. So you share very little DNA with your more distant ancestors.

Mitochondrial DNA (mtDNA) Test

Trace your recent and ancient maternal ancestry.

Who can take it: everyone.

Remember your mitochondria, those little energy-producing structures in your cells? They have their own DNA (called mtDNA) that’s only inherited from your mom.

One cool thing about mtDNA is that it doesn’t recombine much during replication. It can actually stay the same for up to 50 generations.

MtDNA is extremely useful for genealogical research. Often, female ancestors are hard to trace through documents, because they change surnames after marriage. But if you share the same mtDNA sequence with someone, you probably have a common maternal ancestor within 22 generations, or 550 years.

Your mtDNA can also provide clues to your ancient ancestry and how your maternal ancestors migrated across the world throughout human history.

There are several kinds of mtDNA tests available:

The full mitochondrial sequence test (FMS) analyzes all 16,569 base pairs of your mtDNA. It’s the most accurate way to match yourself to relatives and learn about your ancient ancestry.

Other tests sequence only certain regions of your mtDNA known to vary among individuals (HVR1 and HVR2).

A few companies test an array of SNPs from across your mtDNA. This can tell you quite a bit about your traits and ancestry, but can’t match you with relatives.

yDNA Test

Trace your paternal line, including ancient ancestry.

Who can take it: men, though women can have a close male relative test for them.

Of your 46 chromosomes, only the Y chromosome is passed exclusively from father to son. This chromosome undergoes very little recombination during replication. So if you’re a man, your Y chromosome is almost identical to that of your father, grandfather, and so on.

YDNA testing traces paternal lineage in the same way mtDNA traces maternal lineage. You can use the results to match with living relatives and learn about your ancient ancestors’ migration patterns.

There are several types of yDNA tests:

Short tandem repeat (STR) looks at certain repeating DNA sequences that are prone to mutation. This is best for matching with living relatives or ruling out familial connections. Tests can sequence 37, 67, or 111 markers. (Testing more markers increases matching accuracy, but costs more.)

Which Test Is Best?

There are many vendors and options to choose from, and the answer depends on your goals and budget. Serious genealogists often take all three tests with more than one company to get a full picture. Others start with autosomal testing (which is least expensive) and see where it leads them.

Hopefully you’re now feeling confident and excited about taking your DNA test, learning about your heritage, and even locating some of your relatives. Happy searching!